1. Field of the Invention
The present invention relates to the repair of damaged subterranean polyethylene pipes.
2. Description of the Prior Art
With the advent of polyethylene pipes which are commonly joined by fusion bonding, underground repair thereof has posed a significant problem. Once such underground pipes have been damaged, as by accidental encounter with excavation equipment or the like, repair thereof becomes an extremely time consuming and expensive project. This stems from the fact that bonding of such pipes typically requires some degree of relative axial shifting thereof in order to provide for the forming of flush butt ends which must be heated in a plane perpendicular to the axial direction of the pipe and then slid axially together for proper fusion thereof. Early efforts to solve this problem involved excavating laterally outwardly from the underground line at points some 20 feet apart for a distance of some 20 feet and then joining such excavation with another trench disposed parallel to but offset from the main line some 20 feet. Lateral lines are then joined with the main line and joined at their remote extremities with an offset pipe located in such longitudinal trench. It will be appreciated that fusion of the repair lines is facilitated by the fact that the lateral lines may flex apart at their remote ends a distance sufficient to enable joinder of such remote ends by such offset pipe. Such excavation and laying of bypass lines is expensive and time consuming.
Efforts to solve this problem have led to the proposal of polyurethane fittings formed with a tubular body having coupling members bonded to the opposite ends thereof with one such coupling member being formed with interior seals which seal dynamically with a tube received telescopically within the tubular body. A device of this type is shown in U.S. Pat. No. 4,023,831. However, such devices suffer the shortcoming that the seals are exposed directly to the telescopical tube and to any foreign matter, dirt or debris which may be carried on such tube as it telescopes inwardly and outwardly within the body member. Moreover, such devices suffer the shortcoming that when axial tension is applied to the tubular member it tends to neck downwardly in the area of the seal, thus breaking sealing engagement between such seals and the tube and consequently, such couplings have not gained general acceptance in the marketplace.